Optimizing a particular recording system having a magnetic media and a ferrite read and write head entails balancing a number of factors. In order to increase the voltage of a pulse on read back, it is desirable to produce a magnetic media with a large coercive force. It is also desirable to have the magnetic field strength changing at a rapid rate when the magnetic field strength equals the coercive force during the write mode. This produces sharp pulses.
Several factors control the magnetic field. The strength of the magnetic field can be increased by increasing the current level in the core. The core material, however will saturate when the current level reaches a certain level. The level varies depending on the material comprising the core.
In the past, ferrite was used as the core material. The problem with ferrite alone is that the usable coercive force of the medium is limited by the magnetic saturation of the core material. If the current in the windings is increased beyond the ferrite saturation level, the magnetic field strength does not change at a rapid rate when the magnetic field strength equals the coercivity.
To increase the rate of change of the magnetic field, a layer of higher permeability material was placed on the confronting surface of the C-core. This layer prevented the magnetic field from leaving the core at most areas other than at the gap. The current level in the coil could be changed to vary the field strength to a level where the magnetic field strength would change at a rapid rate when the field strength equaled the medium coercivity value.
This represented an advance, however this advance produced additional problems. The junction between the ferrite and the higher permeability metal on the confronting surface creates a ghost gap or another small gap. At the ghost gap flux lines leave the ferrite, enter the atmosphere, and reenter the high permeability layer on the other side of the ghost gap. The flux lines in the atmosphere near the ghost gap cause noise in the magnetic system by magnetizing the magnetic media below the ghost gap. On read back undesirable ghost images or pulses are produced which makes decoding the read data pulses more difficult since the actual data pulses must be differentiated from the ghost images.
Thus, there is a need for a head which can be driven at higher current levels without saturating and which eliminates ghost images when the data is read back from the magnetic media. The absence of ghost images on read back would ease decoding of the signals and the current level could be increased so that the rate of change in the field strength would be rapid when the field strength equaled the coercivity value.